Television receivers and monitors sometimes employ an automatic kinescope bias control system for automatically establishing proper black image representative current levels for each electron gun of the kinescope. As a result of this operation, pictures reproduced by the kinescope are prevented from being adversely affected by variations of kinescope operating parameters which may be caused, for example, by component aging or by component sensitivity to changes in temperature.
A conventional AKB control system includes a current sampling resistor in a kinescope cathode driver amplifier which is coupled to a control amplifier in an AKB feedback control loop for automatically adjusting the kinescope black level. Generally, this is done by sampling the kinescope drive level during a retrace interval, comparing the sample with a reference level and applying a correction current to the driver amplifier in a sense to adjust the black level to a desired reference value. If one employs RC timing elements to generate samples pulses having a given width determined by one time constant and having a delay relative to the retrace pulse determined by another RC time constant, then there may be an undesirable tendency for pulse errors to accumulate due to the use of multiple time constants. Such errors may be caused, for example, by component variations with temperature, age, humidity, etc. and may require occasional readjustment to maintain proper pulse timing.